Hydrogen bonding in plasma-deposited amorphous hydrogenated boron films

Hydrogenated amorphous boron (a-B:H) thin films were prepared by radio-frequency plasma deposition using B2H6 (10%) in H2 as precursor gas. The influence of the substrate temperature and self-bias on the a-B:H film structure was investigated. The boron and hydrogen atom densities were determined by ion-beam analysis. The film structure, especially the bonding of hydrogen to boron, was investigated by Fourier transform infrared (FTIR) spectroscopy. The FTIR data were quantified by using a new formalism which allows a proper calculation of the extinction coefficient from the FTIR spectra. The intensities of the different boron-hydrogen absorption bands were compared with the ion-beam analyzed hydrogen atom densities to determine the absorption strength of the B–H terminal and B–H–B bridge bonds. A non-negligible fraction of hydrogen is shown to be bonded to boron in a B–H–B bridge bond.